Byoung-Hyoun Kim

DIRECT LIQUID CHROMATOGRAPHIC ENANTIOMER SEPARATION OF N-tert-BUTOXYCARBONYL AND N-BENZYL-OXYCARBONYL α-AMINO ACIDS USING POLYSACCHARIDE DERIVED CHIRAL STATIONARY PHASES[1]

The direct enantioseparation of several N-protected t-BOC (tert-butoxycarbonyl) and CBZ (benzyloxycarbonyl) α-amino acids on polysaccharide derived chiral stationary phases (CSPs) is described. Good resolution of N-protected t-BOC and CBZ α-amino acids used in this study has been achieved. Chiralpak AD shows performance superior to other CSPs for the direct separation of the enantiomers of N-t-BOC as well as N-CBZ α-amino acids. The behavior of elution order and the effects of eluent composition for the resolution of N-t-BOC and N-CBZ α-amino acids have been investigated.

Chiral Recognition of N‐Phthaloyl, N‐Tetrachlorophthaloyl, and N‐Naphthaloyl α‐Amino Acids and Their Esters on Polysaccharide‐Derived Chiral Stationary Phases

Enantiomeric separations of N-phthaloyl (N-PHT), N-tetrachlorophthaloyl (N-TCPHT), and N-naphthaloyl (N-NPHT) α-amino acids and their esters were examined on several kinds of polysaccharide-derived chiral stationary phases (CSPs). Resolution capability of CSPs was greater Chiralcel OF than the others for N-PHT and N-NPHT α-amino acids and their esters. In N-TCPHT α-amino acids and their esters, good enantioselectivities showed Chiralcel OG for N-TCPHT α-amino acids, Chiralpak AD for N-TCPHT α-amino acid methyl esters, and Chiralcel OD for N-TCPHT α-amino acid ethyl esters, respectively. From the results of liquid chromatography and computational chemistry, it is concluded that l-form is preferred and more retained with electrostatic interaction in case of interaction between N-PHT α-amino acid derivatives and Chiralcel OF, N-TCPHT α-amino acid derivatives and Chiralcel OD, and N-NPHT α-amino acid derivatives and Chiracel OF. On the other hand, d-form is preferred and more retained with van der Waals interaction in case of interaction between N-TCPHT α-amino acid ester derivatives and Chiralcel OG and Chiralpak AD.

ANALYSIS OF IONIC SURFACTANTS BY HPLC WITH EVAPORATIVE LIGHT SCATTERING DETECTION AND CHARGED AEROSOL DETECTION

High-performance liquid chromatography was employed for the separation of five cationic surfactants and seven anionic surfactants. Detection method was compared with evaporative light scattering detector and charged aerosol detector. Acclaim surfactant and Capcell pak C18 column were selected for the study of separation efficiency. The elution behavior of surfactants on Acclaim surfactant column appeared as both hydrophobic and ionic interactions. In contrast, Capcell pak C18 column showed only hydrophobic interaction. In the case of cationic surfactants, good separation was achieved on an Acclaim surfactant column with methanol-0.1 M ammonium formate (pH 5) eluent. Additionally, anionic surfactants showed good separation results on Acclaim surfactant column with acetonitrile-0.1 M ammonium formate (pH 5) eluent. Optimum separation condition was applied to analysis of cationic surfactants as an antistatic agent in polybutyl acrylate adhesive. In the case of spiked calibration standards into polybutyl acrylate, precision (% RSD) and recovery (%) of five cationic surfactants ranged from 0.6 to 12.8% and from 92.3 to 112.9% for within-a-day assay (intra-batch, n = 3) and from 1.4 to 9.0% and from 97.8 to 111.3% for day-to-day assay (inter-batch, n = 3). The results showed acceptable linearity, precision, and recovery without interfering peaks.

LC‐MS/MS method for the quantification of myo‐ and chiro‐inositol as the urinary biomarkers of insulin resistance in human urine

A simple LC-MS/MS method has been developed and validated for the quantification of endogenous myo- and chiro-inositol in human urine. myo- and chiro-Inositol were completely resolved from other carbohydrates and there were no interference peaks in human urine. The correlation coefficient (n = 3) was greater than 0.9991 over the range 0.05-25.0 µg/mL with the weighted (1/C²) least square method. Precision (%RSD) and accuracy (%RE) were 0-10.0% and 0-6.0% for the intra-day assay (n = 5) and 0-14.3% and 0-10.0% for the inter-day assay (n = 5). myo- and chiro-Inositol have been shown to be stable in human urine stored at room temperature and for three freeze-thaw cycles.

ANALYSIS OF A NEW HERBICIDE (PYRIBENZOXIM) RESIDUES IN SOIL USING DIRECT-EXTRACT-INJECTION HPLC WITH COLUMN SWITCHING

A simple and efficient analysis method of the herbicide residues in soil has been developed and applied to residual analysis of a new herbicide, pyribenzoxim. Extraction and separation were performed in sequential mode by on-line column switching. On-line analysis shows better specificity than off-line analysis does. The analyte was well separated without interference and baseline distortion. Recovery yields for standard spiking were 97.9 ± 1 (S.D.) and 92.1 ± 4 (S.D.) % at the concentration of 0.04 and 0.1 ppm in soil, respectively (n=3). The correlation coefficient was greater than 0.999 over the range between 0.1 and 10/mL. The on-line solid phase extraction (SPE) analysis is described, as compared to off-line SPE analysis.

ENANTIOMER SEPARATION OF N-t-BOC AND N-CBZ α-AMINO ACIDS AND THEIR ESTERS ON POLYSACCHARIDE DERIVED CHIRAL STATIONARY PHASES

Liquid chromatographic enantiomer separation of N-t-BOC and N-CBZ α-amino acid, methyl ester, and ethyl ester derivatives was performed on chiral stationary phases (CSPs) based on polysaccharide derivatives. Good resolution of N-t-BOC and N-CBZ α-amino acid derivatives was achieved on Chiralcel OD, Chiralcel OF, and Chiralpak AD, respectively. Enantioselectivites of N-CBZ protected derivatives were found better than those of N-t-BOC protected derivatives. Moreover, the results of liquid chromatography and computational chemistry suggest that L-form is more retained in the case of carboxylic group of enantiomer locating toward to the inside of grooves, on the other hand, D-form is more retained in the case of alkyl group of α-position of N-protected α-amino acid derivatives locating toward to the inside of grooves.

Gas Chromatographic Method for the Analysis of Organic Acids in the Bio-Catalytic Conversion Process

An analytical method for the quantification of acrylic acid (AA), 1,3-propanediol (1,3-PD) and 3-hydroxypropionic acid (3-HP) in the bio-catalytic conversion process has been developed by gas chromatography. A simple liquid-liquid extraction (LLE) procedure was used in the sample preparation. Organic acid additives such as trifluoroacetic acid were used to improve the extraction efficiency in the LLE procedure. Under optimum analysis conditions, all analytes were satisfactorily separated with no interference. In standard calibration, all correlation coefficients (r(2)) were better than or equal to 0.994. In culture media, the intra-batch precision (% relative standard deviation) and recovery (%) as the average value of the quality control samples were 2.3 and 102.4%, respectively. In addition, the inter-batch precision and recovery as the average value of the quality control samples were 5.0 and 104.0%, respectively. In phosphate buffer, the intra-batch precision and recovery as the average value of the quality control samples were 2.7 and 101.6%, respectively. In addition, the inter-batch precision and recovery as the average value of the quality control samples were 2.9 and 101.7%, respectively. The limit of detection (S/N ratio: 3) and limit of quantification (S/N ratio: 10) were 1.0 and 3.5 µg/mL, 3.0 and 10.0 µg/mL, and 9.0 and 30.0 µg/mL, respectively, for AA, 1,3-PD and 3-HP. Consequently, this method was demonstrated to be acceptable for the quantitative analysis of AA, 1,3-PD and 3-HP in culture media and phosphate buffer.

Gas Chromatographic Method for the Determination of Residual Monomers, 2-(Acryloyloxy)ethyl Isocyanate and 2-(Methacryloyloxy)ethyl Isocyanate, as Curing Agents in an Ultraviolet Curable Adhesive

A gas chromatographic method is described for the determination of residual 2-(acryloyloxy)ethyl isocyanate (AOI) and 2-(methacryloyloxy)ethyl isocyanate (MOI) as curing agents in an ultraviolet curable adhesive. Pre-column derivatization was employed in the determination of AOI and MOI as a means of enhancing the response of the flame ionization detector. Urethane derivatives of AOI and MOI were derived using methanol for 30 min at room temperature. The accuracies (n = 5, three concentration levels) were in the range of 113.4 to 126.7%, and precisions (n = 5, three concentration levels) were in the range of 0.8 to 4.3% for AOI-OMe. Furthermore, the accuracies were in the range of 79.5 to 108.6% and the precisions were in the range of 1.0 to 2.4% for MOI-OMe. The correlation coefficients of six calibration standards were all greater than 0.9999 for AOI-OMe and greater than 0.9998 for MOI-OMe over the range from 10 to 100 µg/mL.

High-Performance Liquid Chromatographic Method of Photoactive Compounds Based on Diazonaphthoquinone for Positive Photoresists

An analytical method for the compositional and quantitative analysis of photoactive compounds (PACs) in positive photoresist (Posi PR) has been developed by high-performance liquid chromatography (HPLC). Under optimum HPLC conditions, various types of PACs consisting of a mixture of isomers were satisfactorily separated with no interference. This method was applied to the quantitative analysis of PACs in Posi PR. All correlation coefficients were better than or equal to 0.998. The precision and accuracy showed no significant deviation and were measured with acceptable values. The intra-batch precision and accuracy (%) of quality control samples ranged from 0.80 to 1.46% and from 101.7 to 102.8%. Consequently, the method was demonstrated to be acceptable for the analysis of PACs in Posi PR. We believe that the HPLC method developed in this work can be used for the compositional and quantitative analysis of PACs in Posi PR.